framework: add optional identifier support
Created by: leandro-arm
This patch creates a new type called fwk_optional_id_t which can be left into undefined. This allows any non-mandatory configuration to be left unassigned reducing code-size and improving upgradability.
Change-Id: I28243b6a9394ce7c476f6574c45e6fc55a9fd6c6 Signed-off-by: Leandro Belli leandro.belli@arm.com